A global period of convulsions 42,000 years ago was the result of an inversion of the Earth’s magnetic field, according to new research.
According to the radiocarbon preserved in the rings of ancient trees, climate degradation, mass extinctions, and even changes in human behavior over several centuries can be directly related to the last time the Earth’s magnetic field changed. its polarity.
The research team has christened the period as Adams Transition Geomagnetic Event (Adams Transition Geomagnetic Event), in honor of science fiction writer Douglas Adams, who famously declared the number 42 the definitive answer to the life, the universe and everything.
“For the first time, we have been able to accurately date the times and environmental impacts of the latest magnetic pole switch,” said Earth scientist Chris Turney of the University of New South Wales in Australia.
“The findings were made possible with New Zealand’s ancient kauri trees, which have been preserved in sediment for more than 40,000 years. Using ancient trees we were able to measure and date the rise in atmospheric radiocarbon levels caused by the collapse. of the Earth’s magnetic field. “
This most recent period of magnetic inversion is known as the Laschamp event, and is what we call a geomagnetic excursion. That’s when the planet’s magnetic poles briefly change places before returning to their original positions. It is one of the most studied magnetic field events on Earth, recorded by ferromagnetic minerals.
It took place about 41,000 years ago and lasted about 800 years. It was still unclear what impact this event had on life on the planet, so when scientists discovered an ancient kauri tree (Agathis australis) in 2019 who had been alive during this time period, took the opportunity to learn more.
This is because trees record atmospheric activity in their annual growth rings. In particular, carbon 14 or radiocarbon can reveal a lot of information about celestial activity.
Radiocarbon only occurs on Earth in traces compared to other naturally occurring carbon isotopes. It forms in the upper atmosphere under the bombardment of space cosmic rays. When these rays enter the atmosphere, they interact with local nitrogen atoms to cause a nuclear reaction that produces radiocarbon.
Since cosmic rays constantly flow through space, the Earth receives a more or less constant supply of radiocarbon. Therefore, a rise in radiocarbon in the rings of trees indicates that the Earth had greater exposure to radiocarbon during that year.
As the Earth’s magnetic field weakens, as it did during the Laschamp event, more cosmic rays enter the atmosphere to produce more radiocarbon. Because of this, scientists had been able to previously determine that the Earth’s magnetic field had weakened to about 28 percent of its normal strength during this 800-year period.
The kauri tree, however, allowed the research team to study the years leading up to the Laschamp event. They discovered that the Adams event took place about 42,200 years ago and the magnetic field was at its weakest point. before the Laschamp event.
“The Earth’s magnetic field dropped to just 0-6 percent force during the Adams event,” Turney explained. “Essentially we had no magnetic field: our cosmic radiation shield had completely disappeared.”
During this time, the Sun’s magnetic field would also have weakened several times, as it also experienced a magnetic inversion as part of its regular cycle. These periods exhibit less sunspot and flare activity, but the Sun’s magnetic field also provides the Earth with a measure of protection against cosmic rays, so that during these solar minimums, cosmic ray bombardment would have increased again.
This weakness of the magnetic field would have caused substantial changes in the Earth’s atmospheric ozone, with dramatic consequences, including thunderstorms and spectacular auroras, and climate change around the world.
“The unfiltered radiation from space ripped air particles into the Earth’s atmosphere, separating electrons and emitting light, a process called ionization,” Turney said.
“Ionized air” fried “the ozone layer, causing a wave of climate change around the world.”
This is consistent with the climate and environmental changes of this era observed in other records around the world, such as the mysterious extinction of Australia’s megafauna.
Interestingly, it also coincides with some of our oldest recorded cave works, prompting researchers to hypothesize that the Adams event may have brought humans inside.
“This sudden change in behavior in very different parts of the world is consistent with an increasing or changed use of caves during the Adams Event, potentially as a refuge from the rise of the ultraviolet U, potentially at harmful levels, during minimums or solar energy particles, which could also explain increased use of the red ocher sunscreen, ”they wrote in their article.
This is a bit speculative, of course, but it suggests that a geomagnetic inversion may be an event that seriously alters the world. And recent evidence has suggested that we are currently on the brink of another.
Researchers say this could be absolutely disastrous in the current climate.
“Our atmosphere is already full of carbon at levels never seen before by humanity. A reversal of the magnetic pole or an extreme change in the Sun’s activity would be unprecedented accelerators of climate change,” Turney said.
“We urgently need to reduce carbon emissions before such a random event occurs again.”
The research has been published in Science.